This method is for determining C5 and lighter diolefins, mono-olefins, and paraffins in olefinic naphthas. Resolved acetylenes, and resolved C6 hydrocarbons, including resolved dienes, are also identified. The method is applicable to selective hydrogenation process feeds, products, and other process streams with similar matrices having a final boiling point of 260°C or lower. Components that do not elute from the chromatographic system under the specified conditions, if present in the sample, are not determined. The lower limit of detection for any compound is 0.01 mass %. The Appendix describes an extension of the method to analyze LPG samples